The present invention relates to devices for shielding bolts, screws and like fasteners from unauthorized access thereto to deter and enable detection of tampering therewith.
Because of the virtually universal use of bolts, screws and the like for all types of fastening uses and the wide availability of wrenches and similar tools adapted for affixation and removal thereof, unauthorized tampering with exposed bolts and screws, particularly in public areas, is a significant, ongoing problem, resulting each year in substantial losses due to theft, vandalism, damage and the like. As only one example of this constantly increasing problem, public utility companies are increasingly experiencing losses due to tampering with usage meters accomplished by the ready removal of the meter cover or other shroud by simple and easy loosening and removal of the retaining bolts or screws. Similarly, vending machines are commonly vandalized by unauthorized tampering with bolts and screws employed in the construction thereof. Many other examples of this problem too numerous to list herein exist.
While careful design engineering enables the minimization of exteriorly accessible bolts and screws in machinery and devices in which unauthorized tampering may be a problem, this solution is not always feasible and, in any event, it is nevertheless inevitable that at least some bolts and screws will be accessible to unauthorized tampering. In the past, various types of covers, caps, plugs and the like have been developed for shrouding otherwise accessible bolts and screws to prevent unauthorized access thereto. Examples of such devices are disclosed in U.S. Pat. Nos. 1,296,165; 3,065,662; 3,174,383; 3,298,272; and 3,492,841. However, it is not believed that such devices have ever been widely accepted and come into common use, presumably because such devices are susceptible to disassembly or other contravention without considerable difficulty.
One such device which has achieved some degree of use is the GUARD-NUT brand device marketed by Rally Enterprises, Inc., of Mill Valley, Calif. The GUARD-NUT device is particularly designed for use in conjunction with bolts used on utility meter devices and basically provides a bolt having a breakaway head adapted to be sheared off the bolt stem upon tightening to a predetermined degree of torque and a sleeve adapted to encircle the remaining end portion of the bolt to prevent access thereto. This device, while effective to prevent tampering with the bolt, also essentially prevents authorized removal of the bolt since the remaining end portion thereof provides no means of accepting any type of common or special tool. Thus, to remove the bolt for authorized purposes, it is necessary to destroy it and its protective sleeve by cutting or drilling.
Many of the prior art anti-tamper devices utilize the shielded bolt or screw to retain the fastener cover or other shielding assembly in place, thereby producing an additional problem in that the shielded bolt or screw may be rotationally untightened and removed by gripping and rotating the fastener cover or other shielding assembly with pliers or a similar conventional tool to frictionally transmit untightening rotation to the retaining head of the shielded bolt or screw. U.S. Pat. No. 4,324,516 discloses a fastener shielding assembly adapted to be mounted rotatably on the lug nut of an automobile wheel so that the shielding assembly cannot be utilized to manipulate the lug nut without breaking the shielding assembly. This device, however, suffers the disadvantage that it is particularly adapted prinipally to use for automobile wheel lug nuts and is not universally adaptable for all sorts of screws, bolts and like fasteners having a stem and an enlarged head. Furthermore, this device suffers the same disadvantage as the above-described GUARD-NUT device in that it must be destroyed in order to remove the shileded lug nut. The aforementioned copending parent application hereto, as well as U.S. Pat. No. 4,065,946, disclose the use of fastener shielding devices in combination with conventional shoulder-type screws or bolts to similarly permit the cover or shielding assembly to rotate about the shielded shoulder bolt or screw to prevent removal rotation of the shielded bolt or screw by clamping action on the cover or shielding assembly. While this type of device provides a simple and reliable arrangement for deterring access to the shielded bolt or screw, these devices also disadvantageously are not universally applicable in that they are ineffective for shielding other conventional bolts, screws and like fasteners which do not have a special shoulder portion and furthermore can be more expensive due to the normally considerably higher cost of special shoulder bolts and screws.
In contrast, the present invention provides a novel apparatus adapted for use universally with all types of conventional bolts, screws and like fasteners of the type having a stem and an enlarged head for shielding the securing head of the fastener to prevent unauthorized access thereto without detectably damaging the components of the apparatus, whereby access to the fastener is substantially deterred on one hand and, in the event tampering occurs, is susceptible of ready detection on the other hand, while the apparatus is also adapted for easy disassembly without total destruction of the apparatus to permit ready access to the fastener head for authorized removal when desired.